Michael Miller, director of the Healthcare Crimes Unit at the Maine Attorney General’s Office, said Thursday that the investigation ended in May 2012. Miller said no charges were filed and that no civil actions have been taken by the state agency against anyone.

The investigation had been focused on prescription practices of pharmacies.

Miller would not discuss any other aspects of the investigation.

The investigation came to light when defense attorneys sought to use one report within the wide-ranging statewide probe to challenge the credibility of former MDEA agent Kirk Guerrette.

Guerrette, who is now a lieutenant with the Knox County Sheriff’s Office, has maintained since the issue was raised publicly that he had not done anything wrong. On Thursday, he issued a written statement, after being told by the BDN that the investigation was over.

“I am glad the truth has finally been revealed and that my family and I can finally put this behind us as my family has been so negatively affected by all the controversy surrounding the AG investigation,” Guerrette said. “It would have been courteous and considerate to hear from the AG’s office personally regarding its conclusion to this investigation.”

Guerrette’s name first surfaced publicly during a March 2011 hearing in Knox County Superior Court, when investigators revealed that 4,200 pages and 42 compact discs of information already had been compiled from the investigation, which had been ongoing since at least 2010.

Miller argued at the March 2011 hearing that the records should not be given out to defense attorneys who wanted them in an effort to find evidence that might discredit Guerrette, who was to be a witness in 44 criminal drug cases.

Miller said last year that a single report that referred to Guerrette was part of a complicated investigation that was far from complete. She said it involved numerous parties.

“In direct competition with defendant’s rights is the compelling interest of HCU in maintaining the confidentiality of its intelligence and investigative information,” Miller wrote in court documents. “Disclosure of the HCU information would prematurely reveal the scope, nature and direction of HCU’s case, allow suspects to construct defenses, and create a possibility of evidence destruction, witness harassment or intimidation.”

The investigation was complex and involved many people, Miller wrote. Even if the people who saw it were sworn to secrecy, it could still get leaked and foil the unit’s work, she wrote last year.

The Healthcare Crime Unit investigates MaineCare fraud and crimes committed by health care providers. The unit would investigate a law enforcement officer only if he were involved in a larger “criminal scheme or conspiracy” that involved a MaineCare provider, Miller said back in March 2011.

Justice Jeffrey Hjelm later ordered that some of the material be turned over to defense attorneys but said it could not be released publicly.

Guerrette had worked as an agent for MDEA, assigned from the Knox County Sheriff’s Office, until December 2010. That December, MDEA Director Roy McKinney sent Guerrette back early to the sheriff’s office for unspecified reasons. He was cleared of any wrongdoing after an internal sheriff’s office investigation, according to Sheriff Donna Dennison, who promoted him to lieutenant.

In his statement on Thursday, Guerrette said, “It would have been courteous and considerate to hear from the AG’s office personally regarding its conclusion to this investigation … but again … as they told me all along … I was just a witness in this investigation. If this is what witnesses have to endure … I do not wish this on anyone. So now that my duties as a ‘witness’ have ended, I look forward to restoring my career, my reputation and family which was so negatively impacted by all of this.”

Defense attorney Jeremy Pratt, who represented some of the defendants on the list of 44 cases, said he thought someone should have been charged as a result of the state investigation. He declined to say who should have been charged.

Defense attorney Joseph Steinberger, who represented one of the drug defendants on the list, said he feels there is a double standard being used by government on drug laws.

“There’s a double standard. If you have enough money, you can get a doctor to write you a prescription, but if you buy the same drug on the black market, you become a felon,” Steinberger said.

He said police officers have a lot of power.

Guerrette said in March that all but three of the 44 criminal cases that were on the list in which he was a witness had been resolved. Pratt said Thursday that he knows most of the cases were settled.

One of the pending cases is that of Christian Neils, 35, of Hope, who is charged with aggravated trafficking in marijuana at his home in Hope in September 2010.

Neils’ attorney Leonard Sharon had sought to throw out a search warrant, arguing that it may not have been granted if the person approving the search warrant had known of Guerrette’s use of prescription drugs.

Justice Hjelm disagreed, however, and in June rejected a request by Sharon to have a full hearing to try to throw out the search warrant. Hjelm stated in his ruling that the only evidence provided was affidavits filed by Sharon that refer to claims by others about Guerrette and his alleged excessive use of the sleep aid Ambien. The judge ruled that some of the information in Sharon’s filings were about Guerrette’s alleged Ambien use at a time that had no bearing on the September 2010 search.

“Other information is little more than ruminations. Some information was not relevant,” Hjelm stated in his order.